This invention relates generally to call model integration in a voice over communications network and is particularly directed to providing access to features external to a given domain by overlaying a call model representation intrinsic to an external domain atop a base call model integral to a pre-specified base domain.
The Internet as a means of voice communication (VoIP) is gaining widespread acceptance at a rapid rate. At the same time, Intelligent Network (IN) services are increasingly being used to enhance the user experience within the context of Public Switched Telephone Network (PSTN) calls. Obvious advantages would be derived by employing the technology and services from the PSTN domain as VoIP-based applications become more widespread, while maintaining access to various network types, i.e., write a service once and use it in different types of networks transparently.
Call handling in any communications system requires the execution of a call processing program that handles state transitions in a finite state machine called the xe2x80x9ccall model.xe2x80x9d These transitions are representative of the events that occurred during the lifetime of the call, and result in the execution of various pre-defined xe2x80x9cactions.xe2x80x9d A call model typically is executed by switches within the network. At certain points within the execution of a call model, some of these actions may result in the firing off of queries to other network components such as Intelligent Network (IN) service control points (SCPs) for more information on how call events are to be treated or how call processing is to be handled, going forward. This scenario brings to the fore two basic requirements for easy access to existing IN services:
a. The call model executing on the switch must be capable of supporting a finite state machine (FSM) that models the states expected of an IN call model, and
b. The entity attempting to query the SCP for access to IN services must use messages specified in some pre-defined, agreed-upon format.
Traditional public switched telephone network (PSTN) switches endowed with IN capabilities (SSPs) satisfy both the above requirements and are capable of performing the following functions:
a. Call processing functions involving signaling to/from end-points, signaling between switches in the path from the originating to the terminating end-point, etc., and
b. Access to IN services hosted off of network components such as the SCP.
Internet protocol (IP)-based switch implementations (the so-called softswitches), however, support an IP-based multimedia call model whose state machine is typically based on protocols such as H.323 and SIP where the states are not IN-compliant. Therefore, there is a need to provide IN service access and reuse for IP end-point subscribers.
The present invention is directed to a novel approach for providing the existing set of traditional public switched telephone network (PSTN)-based Intelligent Network (IN) services to Internet protocol (IP) end-point subscribers. The present invention employs a call model layer that implements the IN call model, but is closely integrated with the IP-based, multimedia call model that runs within the base platform. This integration is achieved through a state-level map between states and the IN call model and the corresponding states in the base call model. The IN call model layer is thus capable of supporting access to IN components so that the existing base of IN services may be easily accessed and the base layer is capable of supporting client-level interaction and event handling. Call state information is shared between the two layers to enable them to operate in synchrony. State transitions made by one call model finite state machine (FSM) are thus reflected in the other.
More specifically, in a traditional IN-capable public switched telephone network (PSTN) a switch or service switching point (SSP) is capable of performing call processing functions involving signaling to/from end-points, signaling between switches in the path from the originating to the terminating end-point, and various other functions. In addition, access to IN services hosted off of network components such as the service control point (SCF) are also provided. While the present invention is disclosed primarily in terms of providing IN services to IP end-point subscribers, this invention is not limited to interfacing these two types of protocols. This invention thus also contemplates interfacing other base protocols such as Session Initiation Protocol (SIP) with other service protocols such as Transaction Capabilities Application Part (TCAP) or Intelligent Network Application Part (INAP), and variations thereof.
In IP-based implementations, the Soft SSP includes a gatekeeper which performs functions such as admission control, bandwidth control, location services, call setup signaling, call processing, etc., for end-points within its zone, when xe2x80x9cgatekeeper routedxe2x80x9d calls are set up. In order to do this, the gatekeeper supports a call model within a finite state machine (FSM) in the SSP that it executes for each call. In order to support access to IN services from IP end-points, the present invention emulates/integrates these functions within/into an IP element. The emulation/integration is accomplished by precise mapping of semantically equivalent states in the IN call model and the corresponding states in the IP-based call model.
By integrating the IN call model layer and the IP-based call model layer, services within the IP domain may also be accessed by the call model layer. Thus, access is provided to both IP-based and IN-based services without constraining the implementation in any way. In addition, integrating the functions for providing access to IN services from IP end-points into an IP element provides a xe2x80x9cportablexe2x80x9d IN call model layer which may be reused across various base platforms with little, if any, modification. This affords wider reuse and greater flexibility for the present invention and an easy evolution path for future developments.